Rivet analyses referenceATLAS_2024_I2784422ATLAS Kaon and Lambda Underlying Event spectra at 13 TeVExperiment: ATLAS (LHC) Inspire ID: 2784422 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
Properties of the underlying-event in $pp$ interactions are investigated primarily via the strange hadrons $K_{S}^{0}$, $\Lambda$ and $\bar\Lambda$, as reconstructed using the ATLAS detector at the LHC in minimum-bias $pp$ collision data at $\sqrt{s} = 13$ TeV. The hadrons are reconstructed via the identification of the displaced two-particle vertices corresponding to the decay modes $K_{S}^{0}\rightarrow\pi^+\pi^-$, $\Lambda\rightarrow\pi^-p$ and $\bar\Lambda\rightarrow\pi^+\bar{p}$. These are used in the construction of underlying-event observables in azimuthal regions computed relative to the leading charged-particle jet in the event. Events with a leading charged-particle jet in the range of $10 < p_\text{T} \leq 40$ GeV are studied using the number of prompt charged particles in the transverse region. Source code: ATLAS_2024_I2784422.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/ChargedFinalState.hh"
5#include "Rivet/Projections/FastJets.hh"
6#include "Rivet/Projections/UnstableParticles.hh"
7
8
9namespace Rivet {
10
11 /// @brief ATLAS Kaon and Lambda Underlying Event spectra at 13 TeV
12 class ATLAS_2024_I2784422 : public Analysis {
13 public:
14
15 /// Constructor
16 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2024_I2784422);
17
18 void init() {
19
20 // Jet finding over all ATLAS inner detector prompt-charged above pT threshold.
21 declare(FastJets(ChargedFinalState(Cuts::abseta < 2.5 && Cuts::pT > 500*MeV), JetAlg::ANTIKT, 0.4), "jets");
22
23 // We will only then use prompt charged at a smaller radius than the jet maximum: 2.5 - R
24 // This is so as to not be biased by charged particles from any jets at larger radii.
25 declare(ChargedFinalState(Cuts::abseta < 2.1 && Cuts::pT > 500*MeV), "promptCharged");
26
27 // But we also have an event-requirement of at least one 1 GeV track somewhere in the inner detector
28 declare(ChargedFinalState(Cuts::abseta < 2.5 && Cuts::pT > 1*GeV), "eventSelection");
29
30 // We take strange particles at a tighter eta still, this was to preserve a high purity from the detector reconstruction.
31 declare(UnstableFinalState(Cuts::pid == PID::K0S && Cuts::abseta < 1.0), "kaon");
32
33 declare(UnstableFinalState(Cuts::abspid == PID::LAMBDA && Cuts::abseta < 1.0), "lambda");
34
35 // All 1D observables used in the creation of final ratios.
36 size_t ih = 1;
37 for (const string& obs : vector<string>{ "pTlead", "nTrans" }) {
38 for (const string& num : vector<string>{ "kaon", "lambda" }) {
39 for (const string& den : vector<string>{ "", "prompt", "kaon", "lambda" }) {
40 for (const string& var : variables) {
41 for (const string& reg : regions) {
42 if (den == "") dualbook(obs, num, var, reg, ih);
43 else dualbook(obs, num, den, var, reg, ih);
44 ih += 2;
45 }
46 if (num == den) break; // nTrans only
47 }
48 if (num == den) break;
49 }
50 }
51 }
52 }
53
54 void analyze(const Event& e) {
55
56 // Require at least one charged particle to be above 1 GeV
57 const Particles& eventSelection = apply<ChargedFinalState>(e, "eventSelection").particles();
58 if (eventSelection.empty()) vetoEvent;
59
60 // We want our leading jet to be fully contained within the ATLAS inner detector, hence cutting jets at eta=2.1 for R=0.4
61 const Jets& jets = apply<FastJets>(e, "jets").jetsByPt(Cuts::absrap < 2.1 && Cuts::pT > 1*GeV);
62 if (jets.empty()) vetoEvent;
63
64 const double jetphi = jets[0].phi();
65 const double jetpT = jets[0].pT();
66
67 // Count the multiplicity and scalar sum-pt of charged particles and strange particles
68 map<string,YODA::Counter> counts;
69
70 // Charged particles up to the max radius allowed for the leading jet
71 const Particles& promptCharged = apply<ChargedFinalState>(e, "promptCharged").particles();
72 for (const Particle& p : promptCharged) {
73 if (p.origin().polarRadius() / mm > 1.5) continue;
74 // Counting prompties
75 const double dPhi = deltaPhi(p.phi(), jetphi);
76 if (dPhi <= PI/3.0) {
77 counts["prompt"s+"towards"s+"n"s].fill();
78 counts["prompt"s+"towards"s+"sumpt"s].fill(p.pT()/GeV);
79 } else if (dPhi > 2*PI/3.0) {
80 counts["prompt"s+"away"s+"n"s].fill();
81 counts["prompt"s+"away"s+"sumpt"s].fill(p.pT()/GeV);
82 } else {
83 counts["prompt"s+"transverse"s+"n"s].fill();
84 counts["prompt"s+"transverse"s+"sumpt"s].fill(p.pT()/GeV);
85 }
86 }
87
88 for (const string& type : vector<string>{"lambda", "kaon"}) {
89
90 // Strange particles up to eta of 1.0
91 const Particles& identifiedFS = apply<UnstableFinalState>(e, type).particles();
92
93 const double RxyMin = (type == "kaon"s? 4*mm : 17*mm);
94 const double pTMin = (type == "kaon"s? 400*MeV : 750*MeV);
95
96 // Loop over Kaon and Lambda particle vectors, apply detector cuts
97 for (const Particle& p : identifiedFS) {
98
99 const double particlePt = p.pT();
100 if (particlePt < pTMin) continue;
101
102 const Particles children = p.children();
103 if (children.size() != 2) continue;
104
105 if (children[0].abseta() > 2.5 || children[1].abseta() > 2.5) continue;
106
107 const double decayDistancePerp = children[0].origin().polarRadius() / mm;
108 if (decayDistancePerp <= RxyMin || decayDistancePerp > 300*mm) continue;
109
110 if (type == "kaon"s && (children[0].abspid() != PID::PIPLUS || children[1].abspid() != PID::PIPLUS)) {
111 continue;
112 }
113 bool lambdaRejected = false;
114 if (children[0].abspid() != PID::PIPLUS && children[0].abspid() != PID::PROTON) lambdaRejected = true;
115 if (children[1].abspid() != PID::PIPLUS && children[1].abspid() != PID::PROTON) lambdaRejected = true;
116 if (type == "lambda"s && lambdaRejected) continue;
117
118
119 const double dPhi = deltaPhi(p.phi(), jetphi);
120 if (dPhi < PI/3.0) {
121 counts[type+"towards"+"n"].fill();
122 counts[type+"towards"+"sumpt"].fill(p.pT()/GeV);
123 } else if (dPhi > 2*PI/3.0) {
124 counts[type+"away"+"n"].fill();
125 counts[type+"away"+"sumpt"].fill(p.pT()/GeV);
126 } else {
127 counts[type+"transverse"+"n"].fill();
128 counts[type+"transverse"+"sumpt"].fill(p.pT()/GeV);
129 }
130 }
131
132 }
133
134 const bool isRestrictedRange = (jetpT > 10*GeV && jetpT <= 40*GeV);
135 const double nTransversePrompt = counts["prompt"s+"transverse"s+"n"s].val();
136
137 // Fill all 1D accumulator histograms
138 for (const string& type : vector<string>{ "kaon", "lambda", "prompt" }) {
139 for (const string& var : variables) {
140 for (const string& reg : regions) {
141 _h["pTlead"+type+reg+var]->fill(jetpT/GeV, counts[type+reg+var].val());
142 if (isRestrictedRange) {
143 _h["nTrans"+type+reg+var]->fill(nTransversePrompt, counts[type+reg+var].val());
144 }
145 }
146 }
147 }
148
149 // Fill the two "per event" normalisation histograms
150 _h["pTlead"]->fill(jetpT/GeV);
151 if (isRestrictedRange) _h["nTrans"]->fill(nTransversePrompt);
152
153 }
154
155 void finalize() {
156
157 for (const string& obs : vector<string>{ "pTlead", "nTrans" }) {
158 for (const string& num : vector<string>{ "kaon", "lambda" }) {
159 for (const string& reg : regions) {
160 // Normalise same-species ratio distributions,
161 // used to obtain ensemble-averaged mean-pT
162 divide(_h[obs+num+reg+"sumpt"], _h[obs+num+reg+"n"], _e[obs+num+num+reg+"n"]);
163
164 // Normalise inter-species ratio distributions
165 for (const string& den : vector<string>{ "prompt", "kaon" }) {
166 if (num == den) break;
167 for (const string& var : variables) {
168 divide(_h[obs+num+reg+var], _h[obs+den+reg+var], _e[obs+num+den+reg+var]);
169 }
170 }
171 } // regions
172 }
173
174 // Normalise per-event normalised distributions
175 // Note: Due to scale(), this must run AFTER the inter-species ratios above,
176 // and that kPrompt has a different normalisation factor to kKaon or kLambda.
177 for (const string& num : vector<string>{ "kaon", "lambda" }) {
178 for (const string& reg : regions) {
179 const double deltaEta = 2.*1.0;
180 const double deltaPhi = 2.*M_PI/3.;
181 const double regionSize = deltaEta * deltaPhi;
182 for (const string& var : variables) {
183 scale(_h[obs+num+reg+var], 1.0/regionSize);
184 divide(_h[obs+num+reg+var], _h[obs], _e[obs+num+reg+var]);
185 }
186 }
187 }
188
189 } // pTlead vs nTrans
190
191 }
192
193 void dualbook(const string& obs, const string& num, const string& var, const string& reg, size_t ih) {
194 const string label = obs+num+reg+var;
195 book(_e[label], ih, 1, 1);
196 if (_h.find(obs) == _h.end()) {
197 book(_h[obs], "_"+obs+"Spectrum", _e[label].binning().edges<0>());
198 }
199 }
200
201 void dualbook(const string& obs, const string& num, const string& den, const string& var, const string& reg, size_t ih) {
202 const string ratio = obs+num+den+reg+var;
203 const string numer = obs+num+reg+var;
204 const string denom = obs+den+reg+var;
205 book(_e[ratio], ih, 1, 1);
206 if (_h.find(numer) == _h.end()) book(_h[numer], "_"+obs+"_"+num+"_"+reg+"_"+var, _e[ratio].binning().edges<0>());
207 if (_h.find(denom) == _h.end()) book(_h[denom], "_"+obs+"_"+den+"_"+reg+"_"+var, _e[ratio].binning().edges<0>());
208 }
209
210 private:
211
212 const vector<string> regions = {"away", "towards", "transverse"};
213 const vector<string> variables = {"n", "sumpt"};
214
215 map<string,Histo1DPtr> _h;
216 map<string,Estimate1DPtr> _e;
217
218 };
219
220 // The hook for the plugin system
221 RIVET_DECLARE_PLUGIN(ATLAS_2024_I2784422);
222
223}
|
